The present invention relates generally to medical technology and more particularly, it relates to through corneal prostheses employed to restore vision to patients with grave cataracts in cases wherein keratoplasty fails.
It is known in the art to employ a through corneal prosthesis comprising a bearing member formed as a disk with a plurality of perforations formed therein carrying a centrally mounted bushing with a threaded hole, and a removable optical cylinder with an external thread threadedly received into the bushing. The known prosthesis is also provided with a temporary removable plug having an external thread corresponding to the thread of the hole in the bushing.
The prosthesis is installed in a two-step operation. At the first step, the cornea is divided into outer and inner layers, the inner layers are perforated and the bearing member whereof the bushing carries the removable plug screwed therein is inserted into the space intermediate the outer and inner layers of the cornea until the bushing is aligned with the perforated hole. The requirement to perforate the inner corneal layers stems from the height of the bushing which far exceeds the thickness of the cornea whereinto the prosthesis is installed.
After the bearing member of the prosthesis has been installed, a suture is applied.
The second stage of the operation is carried out after the bearing member of the prosthesis has been implanted. This step comprises perforating the outer corneal layers above the bushing and substituting an optical cylinder for the temporary plug.
However, with the inner corneal layers perforated at the first stage of the operation, the adhesion of the divided corneal layers is more difficult to achieve and the implantation of the bearing portion is hindered. Further, the perforation provides a route whereby moisture from the anterior chamber may seep into the space between the corneal layers, giving rise to a "false" chamber.